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WPAN/WLAN/WWAN Multi-Radio Coexistence. IEEE 802 Plenary, Atlanta Tuesday, November 13 2007, 9:00 PM . Presenters: Jari Jokela (Nokia) Floyd Simpson (Motorola) Artur Zaks (Texas Instruments) Jing Zhu (Intel)

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wpan wlan wwan multi radio coexistence
WPAN/WLAN/WWAN Multi-Radio Coexistence

IEEE 802 Plenary, Atlanta

Tuesday, November 13 2007, 9:00 PM

Presenters: Jari Jokela (Nokia)

FloydSimpson (Motorola) Artur Zaks (Texas Instruments)

Jing Zhu (Intel)

Sponsored by Stuart J. Kerry (802.11 WG Chair) with support from Roger B. Marks (802.16 WG Chair)

abstract
Abstract

This presentation gives an overview on multi-radio coexistence with radios operating on adjacent and overlapping unlicensed or licensed frequency bands, covering use cases, problem analysis, and possible directions for solution. It shows that coexistence has to consider both proximity and collocation. Collocation imposes big challenges due to limited isolation and various interference sources. Need for cost-effective solution leads to approach where antennas are shared by multiple radios thus introducing the requirement for multi-radio time resource coordination. Today’s solutions are neither effective, nor scalable with number of radios and number of vendors. Standardization efforts are needed to provide information service, command, and air-interface support necessary for addressing coexistence issues.

agenda
Agenda
  • motivation
  • state of the art
  • media independent time sharing
  • conclusion
slide5

Motivation

Near Field Communication

Wi-Fi

A,B,G,N

60GHz

UWB

Bluetooth

GPS

TV- DVB

WiMAX

3G

Many Radios with Limited Spectrum and Limited Space

FM

comparison of wi fi wimax bluetooth

Motivation

Comparison of Wi-Fi / WiMAX / Bluetooth*

Wireless technologies have different sweet spots of operation in terms of coverage, QoS, power, throughput, etc.

*Other names and brands may be claimed as the property of others.

multi radio concurrent usages

Motivation

Multi-Radio Concurrent Usages

WiMAX Coverage

Bluetooth Coverage

Bluetooth Coverage

Wireless Gateway

on the road

Wi-Fi Coverage

Seamless Handover

in home / office

coexistence challenges 1 inter radio interference

Motivation

WiMax

Wi-Fi

GSM 800

CDMA1800

BT

UWB

WiMax

Wi-Fi

GSM 800

CDMA 1800

BT

UWB

GPS

Coexistence Challenges (1): Inter-Radio Interference

Interferer

Victim

Isolation Requirements

Severe Moderate Cautious No-problem

>55db 40-55db 25-40db <25db

coexistence challenges 2 multi radio i ntegration

Motivation

Near Field Communication

Wi-Fi

A,B,G,N

60GHz

UWB

Bluetooth

GPS

TV- DVB

WiMAX

3G

Coexistence Challenges (2): Multi-Radio Integration

FM

  • Antenna sharing is more and more commonly being used for multi-radio integration due to limited space on small form-factor device.
    • Wi-Fi & Bluetooth Integrated Solution
  • What is next? Reconfigurable / Software Defined Radio
  • Multi-radio usage and performance should not be sacrificed
coexistence related ieee standards

State of the Art

Coexistence-related IEEE Standards

Lack of coexistence support in air-interface for emerging WPAN/WLAN/WWAN

multi-radio device

slide11

State of the Art

Overview of Coexistence Solutions

not scalable, and not support component sharing

media independent, and potentially scalable, but needs air-interface support

case study 802 11 802 15 1 time sharing coexistence mechanisms

State of the Art

Case Study: 802.11/802.15.1 Time Sharing Coexistence Mechanisms
  • Basic Ideas
  • per-packet authorization of all transmissions
  • arbitrate the radio activity by priority when collision happens
  • Over-The-Air (OTA) Requirements
  • maintain radio duty cycles at friendly/low level
  • provide flexibility to (re)schedule radio activity
  • forecast schedule for other radios to react

Compressibility

Selectivity

Predictability

[IEEE 802.15.2, 2003]

Table: IEEE 802.15.1 packet types

Difficult to support TS coexistence

Commonly used in cellular headset

Most friendly to TS coexistence

PTA: Packet Traffic Arbitration, AWMA: Alternating Wireless Medium Access

SCO: Synchronous Connection-Oriented, ACL: Asynchronous Connection-Less, HV: High Quality Voice

what is the problem with time sharing ts

State of the Art

What is the Problem with Time Sharing (TS)?

Device A

Device C

  • Radio activities may not always be locally controllable
    • 802.11: frame may arrive at any time due to random access
    • 802.16: base station to schedule all the activities of a mobile station
    • 802.15.1: master to schedule but usually power constrained
  • Challenging to provide desirable performance on each of the coexisting radios
    • the performance on one radio is usually protected at the cost of the other radio’s performance

Inter-Radio

Interference

Wireless

Network 1

Wireless

Network 2

TX

TX

(Multi-Radio)

Device B

RX

RX

today s ota techniques for time sharing coexistence

State of the Art

Today’s OTA Techniques for Time Sharing Coexistence
  • Common Problems
  • Inexplicit, after-thought and case-specific, and difficult to be applied to new usages
  • Low reliability and low efficiency due to lack of explicit / reliable support in air-interface

UAPSD: unscheduled automatic power save delivery, CTS: Clear-To-Send, eSCO: extended SCO

limitations of uapsd

State of the Art

Limitations of UAPSD

Difficult to predict T4 due to Access Point implementation specifics, varied channel access time and transmission time

  • Unpredictable AP response time for downlink traffic
  • Not applicable to AP experiencing jamming co-located interferences
    • wireless residential gateway
  • Not efficient to use with asymmetric or heavy traffic (e.g. data, video, etc.)
    • video streaming
    • additional overhead due to trigger frame / PS poll
per performance with uapsd

State of the Art

PER Performance with UAPSD
  • Two .11g Links: VoIP (54Mbps)+ Data (Variable)
    • Interference Period: 6 Bluetooth Slots
  • High (up to 40%) downlink PER due to varied channel access time

a) Uplink Trigger

b) Downlink Data

limitations of 802 16e sleep mode

State of the Art

Limitations of 802.16e Sleep Mode

Class A

Listening

Sleep

  • Not applicable to multiple interferences reports with different pattern
  • Coarse granularity: frame duration (5ms)
    • Bluetooth Slot: 625 us
    • inefficient when only a small portion is interfered
  • Little flexibility
    • Rx and Tx may be treated differently in coexistence
  • Little reliability & Best-Effort
    • coexistence is about avoiding interference and protecting radio activities
    • reliability is important, and time info needs to be respected
  • Other limitations
    • Not applicable to other states (e.g. network entry)
    • may be intended for other usage (scanning)

Class B

Sleep Mode

Coexistence

Inactive

Active

recap why time sharing

Media Independent TS

Recap: Why Time Sharing?
  • Power / Frequency control is ineffective in mitigating wideband co-located interference
    • further limited by other network factors, e.g. channel, link budget, etc.
    • not support component sharing due to integration
  • Low duty-cycle radio activity is possible
    • broadband / MIMO techniques  more bits/s
      • 802.11: 20MHz  40MHz
      • 802.16: 5MHz  10MHz  20MHz
      • MIMO: 1x2  2x2  4x4
  • Media independent description of radio activity is possible
  • High Data Rate
  • Coverage
  • QoS Support
  • Security
  • Low Power
  • Mobility
  • Multi-Radio Coexistence

Design Considerations of

an Air-Interface

media independent description of radio activity

Media Independent TS

Media Independent Description of Radio Activity

t

Active

Inactive

Type 1: Duty Cycle

T

P

Type 2: Bitmap

1

0

0

0

1

1

0

0

0

1

1

0

0

B

  • t: starting time of an activity cycle
  • T: duration of each activity burst (Type 1)
  • B: bitmap (Type 2)
  • x: time unit
  • P: burst period – i.e., interval between bursts
  •  both type 1 and type 2 descriptions can be periodic, and P indicate the duration for one period
  • N: number of bursts
  • s: type of activity: TX, RX, or both
explicit coexistence support

Media Independent TS

Explicit Coexistence Support
  • Explicit Coexistence Feedback
    • heterogeneous time granularity
      • Bluetooth slot = 625us, 802.11 Time Unit = 1024us, 802.16 symbol = 102.9us, 802.16 frame = 5ms

Requirement 1: scalable time unit

    • synchronization
      • clock drift
      • period mismatch

Requirement 2: information update & feedback control

  • Explicit Coexistence Protection
    • reliable and beyond best-effort
    • link adaptation, scheduling, etc.

Requirement 3: reliable protection

Goal: Media Access Control with multiple constraints

    • QoS, channel condition, traffic arrival, multi-radio coexistence, …
time sharing of 802 16 802 11 802 15 1 activities

Media Independent TS

Time Sharing of 802.16 / 802.11 / 802.15.1 Activities

3.75ms

625us

M

S

802.15.1 HV3

(33%)

5ms

802.16 frame

Structure

DL

UL

DL

UL

DL

UL

802.16 Activity (58%)

802.11 Activity (20%)

15ms

Explicit coexistence support enables seamless time sharing of radio activates, reduces the collisions, and ensures desirable performance on individual radio

Note: the pattern may change over time if radios are not in sync

what is the benefit

Media Independent TS

What is the benefit?
  • Better User Experience
    • support more multi-radio concurrent usages
    • cheaper / smaller device without sacrificing functionality & performance
  • More efficient usage of wireless medium and spectrum
    • prevent ill-guided air-interface behavior
    • reduce frame loss and improve reliability
    • seamless interaction among radios
  • Easier and lower cost integration of multiple wireless technologies
    • unified interface / signaling
    • scale to number of radios and number of vendors
slide23

Media Independent TS

802.11v – Co-located Interference Reporting

STA

AP

  • Simple protocol enables terminal to indicate it is using several radios simultaneously and performance of WLAN RX is degraded
  • Report allows terminal to indicate interference time characteristics, level, and other information
  • Automatic reporting is supported, i.e., whenever STA realize co-located interference is changed it can send Report to AP
  • AP can use reported information several ways, 1) it can schedule DL transmissions not to collide with interference slots and 2) it can use information to adjust e.g., rate adaptation and retransmission logics

Co-located Interference Request

Other radio operation is started causing performance degradation

Co-located Interference Report

Other radio operation is stopped

Co-located Interference Report

beyond ieee

Media Independent TS

Beyond IEEE
  • Wi-Fi Alliance Converged Wireless Group (CWG) is working to extend CWG RF Test Plan to cover Bluetooth / Wi-Fi / Cellular coexistence testing
  • Bluetooth SIG is defining feature requirements for coexistence with broadband wireless access technologies, and Telephony Working Group (TWG) is currently working towards publishing a whitepaper to address Bluetooth/WiMAX coexistence
  • WiMAX Forum Coexistence Ad-Hoc has reviewed contributions for WiMAX-BT and WiMAX-Wi-Fi coexistence from Motorola, Altair-Semiconductor, Nextwave and others.
    • Coexistence based on the ‘perceived concurrency’ approach
    • Key enabler is power save mode of WiMAX/Wi-Fi for time sharing and BT MAC retransmission capability
    • Currently working on harmonizing on the key WiMAX system requirements to support time sharing at MAC level
summary

Conclusion

Summary
  • Multi-radio concurrent usage is becoming the norm, and coexistence is the limiting factor
  • Existing approaches are ineffective
    • limited true concurrency (due to cost, size, etc.)
    • best-effort perceived concurrency
  • Media independent time-sharing is promising, but coexistence-awareness in air interface is the must
    • explicit coexistence feedback / protection
  • Is a more coordinated approach to support coexistence in wireless necessary, or even possible?
    • http://www.youtube.com/watch?v=Rh0awIw7PNY
call to action

Conclusion

Call to Action
  • Develop standard-based, scalable, and reliable coexistence solutions, considering the following issues
    • heterogeneous time granularity
    • synchronization
    • reliable protection
  • Add explicit coexistence support to individual air interface to enable
    • Predictability: forecast activity for other radios to react
    • Compressibility: maintain radio duty cycles at friendly level
    • Selectivity: provide flexibility to (re) schedule activity